Purpose: The purpose of this retrospective study was to assess the diagnostic utility of the second-look ultrasound (SLU) to see if the number of biopsies in patients with MRI BIRADS (Breast Imaging Reporting and Data system) 0,3,4,5 could be reduced.

Materials & Methods: A retrospective review was performed of the records of patients, who underwent a MRI of the breast in the general hospital of Vienna (AKH Wien) between January 1st , 2013 and December 31st, 2013. 94 patients with 103 lesions were included in our study. All of these lesions were found on MRI and subsequently examined with an ultrasound (US). All lesions were correlated and most of them (90/103) had a biopsy taken. The remaining lesions underwent Follow-up (FU) for at least one year.

Results: 57 (55,3%) of the 103 lesions showed a correlate on ultrasound. 17 of the correlated lesions were malignant (29,8%). Most correlated lesions were masses. (38/57, 66,7%) Our findings showed that distinguishing between malignant and benign lesions via US is possible. The results were significant for the following morphological features: form, orientation, margins, architectural distortion, hyperechoic rim/ edema. Furthermore, if a lesion is BIRADS 2 in SLU, then a biopsy does not have to be taken, as all lesions with BIRADS 2 in our study were benign. Thus 30% of unnecessary biopsies could be avoided. If lesions with SLU BIRADS 3 would not be taken biopsies from, then 60% of unnecessary biopsies could be avoided, however, 6% of malignant tumors would be overlooked.

Conclusion: SLU is a useful tool to differentiate between benign and malignant lesions in ultrasound. Its diagnostic utility can prove useful to avoid biopsies in lesions with BIRADS 2.